To begin our analysis, we elucidate the behaviour of a surfactant-laden system under the conditions ascribed to the `base' case (refer to §REF ) and compare it to that of surfactant-free interfaces. In order to isolate the effects of lower surface tension from those arising from Marangoni stresses on the encapsulation dynamics, we have set up an additional case, denoted by \(|\tilde{\tau }_{m}| = 0\) , in which we have suppressed the last term on the RHS of Eq. (REF ) to
inhibit Marangoni stresses while simultaneously allowing the reduction of surface tension. Figures REF (a)-(b) show the shape of the liquid cavity and a few other characteristics along its interface at \(\tilde{t} = 2.22\) . For the sake of clarity, we have duplicated the plots of interfacial shape on both column panels. Examination of the plots uncovers an almost surfactant-free interface at the liquid cavity for \(|\tilde{\tau }_{m}| = 0\) , which exhibits a significant drop in \(\tilde{\Gamma }\)  going from the edge to the interior of the cavity in the stream-wise direction and a slight surge after surpassing the incipient pinching neck. This rapid loss of surfactant for \(|\tilde{\tau }_{m}| = 0\) , as opposed to the Marangoni-supported case, \(|\tilde{\tau }_{m}| > 0\) , is explained by noticing that the operating conditions of the base case promote surfactant desorption (large \(Da\)  and small \(k\) ) as \(\tilde{\Gamma } \rightarrow 1 \)  (see Eq. (REF )) as well as slow interface surfactant diffusion (large \(Pe_{s}\) ). Reverting back to the remarks by [1]}, [2]}, the motion of the bubble prompts surfactant accumulation at the back due to drag forces from the liquid phase, partially counteracted by Marangoni stresses in the opposite direction for \(|\tilde{\tau }_{m}| > 0\) . The absence of Marangoni stresses in the \(|\tilde{\tau }_{m}| = 0\)  case leads to a continuous process of local surfactant accumulation at the back and desorption into the bulk, depleting the interface of surfactants.
